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%I #10 Mar 13 2020 20:37:03
%S 1,1,2,1,2,2,1,3,3,2,2,1,4,2,3,2,4,2,3,1,4,3,4,3,3,4,4,3,3,3,2,4,3,3,
%T 3,3,4,4,5,3,4,2,4,2,4,2,3,4,4,5,5,3,5,1,6,3,4,4,5,4,6,2,3,6,6,4,6,3,
%U 8,2,5,5,5,3,2,3,7,2,5
%N Number of prime factors of form cn+1 for numbers 7^n-1
%H S. Mustonen, <a href="http://www.survo.fi/papers/MustonenPrimes.pdf">On prime factors of numbers m^n+-1</a>
%H Seppo Mustonen, <a href="/A182590/a182590.pdf">On prime factors of numbers m^n+-1</a> [Local copy]
%e For n=9, 7^n-1=40353606=2*3^3*19*37*1063 has three prime factors of form, namely 19=2n+1, 37=6n+1, 1063=118n+1. Thus a(9)=3.
%t m = 7; n = 2; nmax = 80;
%t While[n <= nmax, {l = FactorInteger[m^n - 1]; s = 0;
%t For[i = 1, i <= Length[l],
%t i++, {p = l[[i, 1]];
%t If[IntegerQ[(p - 1)/n] == True, s = s + l[[i, 2]]];}];
%t a[n] = s;} n++;];
%t Table[a[n], {n, 2, nmax}]
%K nonn
%O 2,3
%A _Seppo Mustonen_, Nov 22 2010
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